The present invention relates to a resin case required to be gas-permeable and waterproof, such as a connector-integrated case, etc. housing electric and electronic parts inside.
Circuits including electronic parts such as transistors, etc., and electric parts such as motors, etc. used for computers and their peripherals, are designed on substrates. These substrates, etc. are housed in resin cases (hereafter called xe2x80x9cconnector-integrated casesxe2x80x9d) wherein connectors are integrally formed. Terminals connected to the substrates, etc. protrude from the connectors to the outside of the boxes so that the terminals can be attached to other parts through the connectors.
FIG. 13 is a perspective view of a conventional connector-integrated case 100.
FIG. 14 is a cross-sectional view of a connector-integrated case 100xe2x80x2 having the same construction as the connector-integrated case 100 except that it has a through hole 500 provided in a lid 300, and is equivalent to a cross-sectional view along the line 14xe2x80x9414, in FIG. 13.
The connector-integrated case 100 comprises a box 200 and a lid 300 made of resin such as plastic, etc. Inside a connector C provided on one side of the box 200, there is a plurality of terminals T protruding from within to the outside of the box 200 (see FIG. 14).
This terminal T is connected, at one end, to a circuit of a substrate B secured in the box 200 and is attachable, at the other end, to another member through the connector C.
After securing a substrate B inside the box 200, a seal packing (not shown) is placed between an end face of the box 200 and the lid 300. Then, the box 200 and the lid 300 are secured with screws, etc (not shown).
The connector-integrated case 100 like this has to be completely watertight so that moisture may not enter inside.
When there is communication between outside air and the inside of the connector-integrated case 100, conditions of the outside air such as outside air temperature and humidity, etc. may influence the substrate B inside the connector-integrated case 100.
In particular, when humid outside air is taken into the connector-integrated case 100, metal parts such as circuits, etc. of the substrate B are corroded by moisture contained in the outside air, often causing electrical contact failures.
Therefore, the connector-integrated case 100 must be highly airtight.
On the other hand, when electric and electronic parts in use inside the connector-integrated case 100 generate heat and the temperature inside the connector-integrated case 100 increases, the inside air may expand to produce high pressure. Further, under certain conditions, the internal pressure may become lower than atmospheric pressure, that is, it may become subatmospheric.
In order to cope with the thus-produced difference in pressure between the interior and exterior of the connector-integrated case 100, it is necessary to provide a through hole in the connector-integrated case 100. However, provision of such a through hole Inevitably lowers the waterproof quality and airtightness.
Therefore, in the past, as shown in a cross-sectional view of FIG. 14, a through hole 500 is formed in an upper surface of the lid 300 or in a side face of the box 200. The through hole 500 was covered with woven fabric, etc. preventing moisture and oil content from passing through, and allowing only air to pass, to equalize the internal and external pressures while maintaining a waterproof quality and airtightness.
An example of a woven fabric preventing moisture and oil content from passing through and allowing only air to pass is a porous film 400 made of fluorocarbon resin, etc., which is bonded to the box 200 or to the lid 300 by a double-sided tape or by an adhesive.
Since the porous film 400 covering the through hole 500 is made of fluorocarbon resin and the like, the double-sided tape and adhesive, etc. cannot achieve sufficient adhesion, and, as a result, the porous film 400 sometimes peels in use.
Therefore, in a certain connector-integrated case, the porous film 400 is cut into a circular shape and fitted into a metal ring, which is crimped to hold the porous film 400. Then the porous film 400, fitted in the metal ring, is secured to the required position on the box 200 or the lid 300 by insert molding or further crimping.
The porous film 400 is sometimes bonded at the required position on the box 200 or lid 300 by heat sealing or laser seizing.
However, it requires processing time to crimp a metal ring to the periphery of the porous film 400. Further, excessively strong crimping gives rise to the problem of damage to the porous film 400.
Further, bonding the porous film 400 by heat sealing or laser seizing, requires special equipment, resulting in additional cost. Also, during such procedures, it is difficult to locate the porous film 400 at the proper position with respect to the through hole 500. Further, since it is not possible to exert pressure to the porous film 400, sufficient bonding strength cannot be obtained.
In accordance with the invention, a through hole is provided in a sealed resin case, and the through hole is covered with a water/oil-repellent film, which is bonded to the resin case when the resin case is injection-molded. The resin case comprises a box and a lid covering an opening of the box, and the through hole is provided either in the box or in the lid. The water/oil-repellent film is a porous film and is preferably bonded to the resin case by causing the molten resin to enter the pores of the porous film. In a preferred embodiment, the water/oil-repellent film is made by laminating a backing comprising a thermoplastic material and a porous film, and the backing is melted so that it is bonded to the resin case. The joint of a periphery of the through hole and the water/oil-repellent film preferably form a U-shaped cross-section.
In accordance with another aspect of the invention, a die assembly for manufacturing a resin case comprises a first die having an inner surface and an annular protrusion on its inner surface, and a second die having a cylindrical protrusion receivable in the annular protrusion. A water/oil-repellent film is fitted into a recess surrounded by the annular protrusion of the first die, and when the first and second dies are closed the resin used to form the resin case is injected between the two dies. In a preferred embodiment, a pocket is provided either in the recess of the first die or in an end face of the protrusion of said second die, or in both the recess and the end face.
Since the through hole provided in the resin case of the present invention is covered with a water/oil-repellent film, communication of air is provided between the inside and outside of the case but moisture, etc. in the atmosphere do not enter the case. Also, since the water/oil-repellent film is bonded to the resin case when the resin case is injection-molded with molten resin, it is not easily peeled. Further, by using a die of the present invention, the water/oil-repellent film can be integrally bonded when molding the resin case.